"And He was giving orders to them, saying, 'Watch Out! Beware of the leaven of the Pharisees and the leaven of Herod."' (Mark 8:15)

Leaven is budding yeast. It's scientific name is Saccharomyces derived from the Latinized Greek meaning "sugar mold" or "sugar fungus", used since ancient times in baking and brewing. A very small amount of yeast or leaven will thoroughly permeate bread dough. In the Bible, leaven is often used as a synonym for sin that can increase exponentially corrupting Christians and Churches; "A little leaven leavens the whole lump of dough." (Galatians 5:9)

The leaven of the Pharisees is legalism, which is a perversion of the true Gospel of the Lord Jesus Christ substituting self-justification for the justification provided by God through the cross of Jesus Christ. Like Cain, many self-righteous people today vainly try to worship God on their own legalistic terms; "But in vain do they worship Me, teaching as doctrines the precepts of men." (Mark 7:7). The Jewish Pharisees were the religious rulers in Israel. In their pride they believed that because they were Jews, descendants of Abraham, they were justified before God. In their self-righteousness, they believed their many offerings, sacrifices and observance of myriad religious traditions pleased God. As Paul wrote concerning his Jewish brethren; "For not knowing about God's righteousness and seeking to establish their own, they did not subject themselves to the righteousness of God." (Romans 10:3)

The leaven of Herod is licentiousness, a false doctrine that presumes on the grace and mercy of God while embracing the secular world;"Do not love the world nor the things in the world. If anyone loves the world, the love of the Father is not in him." (1 John 2:15) Like many people today who claim to be Christians, the Jewish Herodians were self-righteous hypocrites;"...ungodly persons who turn the grace of our God into licentiousness and deny our only Master and lord, Jesus Christ." (Jude 4)

The Church is under relentless attack by those who teach these false doctrines, promoting the leaven of the Pharisees and the leaven of Herod; "But false prophets also arose among the people, just as there will also be false teachers among you, who will secretly introduce destructive heresies, even denying the Master who bought them..." (2 Peter 2:1). Watch out! Beware! Maranatha!